%% 
%%  The LaTeX Graphics Companion, 2ed (first printing May 2007)
%% 
%%  Example 6-3-4 on page 368.
%% 
%%  Copyright (C) 2007 Michel Goossens, Frank Mittelbach, Denis Roegel, Sebastian Rahtz, Herbert Vo\ss 
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 

\documentclass{ttctexa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{207.83385pt}
\StartShownPreambleCommands
\usepackage{pstricks,pst-tree}
\StopShownPreambleCommands
\begin{document}
\Large
\pstree[linewidth=0.2pt,nodesepB=3pt]{\TC*}{%
   \Tr{a} \Tr{$\hat{X}$}
   \Tr{b} \Tr{x}}
\quad
\pstree[linewidth=0.2pt,nodesepB=3pt]{\TC*}{%
   \TR{a} \TR{$\hat{X}$}
   \TR{b} \TR{x}}
\end{document}